Modifying a special user page on Wikipedia can make your browsing session more informative with dynamic tooltips that preload relevant bits when you mouse over article links. There's no bookmarklet, extension or third party web site required: simply add some code to your monobook.js (a special Wikipedia user page you must be logged in to access), and voila! You've got killer tooltips wherever you log in to browse the 'pedia. Thanks, JackHynes!